During labour, a fetus may experience oxygen deprivation that can produce permanent neurological damage. Cerebral palsy (CP) is a permanent neurological condition characterised by neuromotor spasticity and often associated with seizures and or mental retardation. In severe forms the child may be unable to crawl, have frequent seizures and severe mental handicap. Brain injury from insufficient oxygenation of the baby during labor leading to cerebral palsy is a condition obstetricians wish to avoid. Typically, since the fetus is not easily accessible and therefore evaluation is based on indirect observations, the medical team evaluates indirect signs of insufficient oxygenation of the baby during labour and may intervene with various diagnostic or therapeutic options to avoid serious fetal compromise.
One of the most commonly used methods to evaluate fetal tolerance to labour is analysis of the fetal heart rate by using electronic fetal monitors. These monitors measure both the fetal heart rate and the mother's uterine contraction pattern. They produce a paper print out of the tracing over time. Historically, the clinical staff used visual methods to study the tracings and from this deduce the degree of fetal well being in regards to tolerance to labour or pre-labour conditions. Abnormal patterns can lead to interventions such as more diagnostic tests, induced delivery of the baby or delivery by cesarean section. The features of the fetal heart rate that are used by clinicians include baseline, accelerations, deceleration and variability of the fetal heart rate.
A deficiency with the above described method is that it does not allow to objectively quantify multiple features of tracings over time since the analysis of the strip by the doctor or nurse is visual and therefore subject to imprecision and normal human biases. Physicians show great variation in how they measure, label and interpret fetal heart rate patterns, particularly when the patterns are measured only by visual inspection of the paper recording. While doctors and nurses are trained and presumably competent in their ability to assess the strip, there can be differences of opinion that may result in different interventions being done to the patient. There is often no suitable confirmation of the preoperative diagnosis that can be used to objectively validate the doctor's decision.
The issue of whether severe neurological damage could have been prevented with a suitable diagnosis is the issue of several lawsuits in the United Kingdom and in the United States. Due to the lack of objective and reliable data, the actions of the health care team are frequently considered not defensible and several cases are settled out of court. Irrespective of the exact proportions of preventable cases, the total malpractice cost born by obstetricians is staggering. Total annual estimated cost by the Florida Neurologic compensation Board for the labor & delivery related injuries or death was (no fault cost 27.5$ million per year). Births in Florida represent 4% of the total US births. Extrapolating these rates to the entire United States, the cost of birth related brain injury is approximately 650 million USD annually without accounting for the human cost. For additional information pertaining to the above, the reader is invited to refer to Frank A. Sloan, PhDa, Kathryn Whetten-Goldstein, PhDb, Gerald B. Hickson, MDc, The influence of obstetric no-fault compensation on obstetricians' practice patterns, American Journal of Obstetrics and Gynecology September 1998, part 1 • Volume 179 • Number 3 • p671 to p676 whose contents are hereby incorporated by reference.
A further difficulty in the study of this problem is the relative rarity of serious fetal compromise, both due to its natural low incidence and the fact that the medical team will intervene to prevent its full development whenever there is an indication of it beginning. The difficulty inherent in studying a rare event has been addressed by substituting more commonly observed early new-born outcome characteristics that are related to permanent birth related neurological damage. Examples of these more commonly observed outcomes are low Apgar scores, (a 10 point measure of vigor at birth), or rates of caesarean section for fetal distress. A further extension of this concept is to use even simpler measures such as a scoring of the fetal heart rate record and placing it in various categories based on the cumulative score (Krebs, Fischer scores).
A deficiency of methods of the type described above is that the prognosis of babies with these outcomes e.g. low Apgar scores, caesarean section for fetal distress, low Fisher or low Krebs scores, is generally very good. These tests do not allow an adequate level of discrimination between babies who have poor prognosis and those with a good prognosis.
In the context of the above, there is a need in the industry to provide a method and device for classifying a condition of a fetus that alleviates at least in part problems associated with the existing methods.